1. Field of the Invention
The present invention relates generally to medical devices and methods for their use. More particularly, the present invention relates to methods and devices for treating benign prostatic hyperplasia by applying low frequency vibration to prostatic tissue.
Benign prostatic hyperplasia (BPH), the most common benign neoplasm in males, is a chronic condition that increases in both incidence and prevalence with age. It is associated with progressive lower urinary tract symptoms and affects nearly three out of four men by the seventh decade of life. Benign prostatic hyperplasia is characterized pathologically by a cellular proliferation of the epithelial and stromal elements within the prostate gland P (FIG. 1). As the prostate enlarges, an encapsulating layer of tissue surrounding it inhibits outward expansion, causing the prostate to press against the urethra U like a clamp and also causing a thickening of the bladder wall. The bladder begins to contract even when it contains small amounts of urine, causing more frequent urination. Eventually, the bladder weakens and loses the ability to empty itself, so some urine always remains in the bladder. The narrowing of the urethra and partial emptying of the bladder cause many of the problems associated with BPH.
BPH may be treated with drugs, surgically, or with newly developed minimally invasive techniques. Of particular interest to the present invention, the surgical techniques typically involve resection of tissue in a procedure referred to as transurethral resection of the prostate (TURP). In TURP procedures, a resection blade or tool is introduced through the urethra and employed to resect or core tissue through the urethral wall. While often effective, the procedure is painful, has a relatively long recovery, and frequently has side effects such as incontinence and impotence. More recently, less invasive procedures have been developed. In one, referred to as transurethral microwave thermotherapy (TUMT), a microwave antenna is introduced through the urethra and directs microwave energy to heat the prostate to destroy tissue. The heat, however, presents a substantial risk of injury to the urethral wall, even when measures are taken to provide cooling. A second new procedure, referred to as transurethral needle ablation (TUNA), relies on transurethral introduction of a catheter and advancement of a radiofrequency needle into the prostate. While theoretically exposing the urethral wall to less heat, there is still a risk of injury to the urethra, although fewer side effects are observed. Nonetheless, the recovery time for the injured tissue can still be considerable and the use of the radiofrequency energy presents certain risks to the patient.
For these reasons, it would be desirable to provide improved methods and systems for treating benign prostatic hyperplasia (BPH). Such methods and systems should minimize the risks and side effects associated with BPH treatment and preferably have a shortened recovery time. In particular, the risk of incontinence and impotence should be greatly reduced and preferably eliminated entirely. It would be still further desirable if the methods and systems did not rely on necrosing tissue, thus avoiding the inflammatory and other responses initiated by tissue necrosis. The methods and systems should be reliable, low cost, and effective. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
U.S. Pat. No. 5,380,273 describes a low frequency vibrating catheter used to disrupt clot in the vasculature. Patents describing transurethral prostate treatments include U.S. Pat. Nos. 4,813,429; 4,967,765; 5,330,518; 5,419,763; 5,454,782; 5,496,271; 6,123,083; 6,389,313; 6,517,534; 6,746,465; and 7,261,710.